This invention relates to the treatment of tumors in animal hosts, such as in human beings, and in particular provides a technique for destroying tumors without injury to surrounding normal tissue.
It is a fundamental object of the present invention to provide a suitable method and apparatus that can be applied to the heat treatment of tumors at varied locations within the body of the animal host, particularly when that host is a human being, such that the treatment can be completely monitored, that is, the change in the tumor can be observed in real time and corrections taken if required. Moreover, another primary object is to enable extremely efficient coupling of RF energy to a patient's body such that there is not significant heat absorption in the fatty tissues, but rather only at the site of the tumor or cancer itself.
Reference to the aforesaid patent applications, particularly application Ser. Nos. 643,661 and 595,094, will make clear that tumors have been destroyed in humans by heating the portion of the body containing the tumor so that the temperature of the tumor is raised to a point at which it becomes necrosed, that is, at or above a temperature of about 50.degree. C. The underlying principle for achieving this objective is the fact that when the tumor containing portion of the body is heated by applied radio frequency electromagnetic radiation, the tumor is heated differentially, i.e., to a greater extent than normal tissue such that the temperature of the normal surrounding tissue can be kept below 40.degree. C.
The basic reason that the technique described in the aforesaid applications has been effective is that the blood flow through carcinomas and other neoplasms is sluggish. While tumors possess an angiogenetic factor which initiates the formation of new blood vessels, these however are capillaries which offer great resistance to blood flow.
From experiments which have been conducted, it turns out that when the tumor or malignancy is especially deep-seated and difficult to affect with RF energy because of surrounding fatty tissue, the radiation sometimes has to be of such intensity and to be applied for such an extended period of time that, although the desired differential heating of the tumor is accomplished, yet the surrounding normal tissue is unavoidably thermally damaged.
However, it has been discovered that successful treatment can be effected in the aforesaid difficult cases such that excessive heating or thermal damage to the surrounding tissue is avoided by providing apparatus for moving the applicator plates or discs in an orbital manner whereby the tumor to be treated always lies on an axis between the applicator plates. As a result, the radio frequency energy is focused or concentrated on the tumor but because of the orbital movement of the applicators the energy is not being continuously applied to the same confined area within the patient's body, that is, to the tissue and organs immediately surrounding the tumor. Instead, the applied energy is swept over a comparatively large core or volume so as not to affect the surrounding body tissue adversely.
Essentially then, the present invention improves upon apparatus and techniques previously developed by the present inventor. In those previously developed techniques which can be appreciated by reference to the previously recited patent applications, it was generally understood that a variety of kinds of applicators could be applied to the patient's body if desired. These applicators are, of course, normally insulated and are placed on opposite sides of the portion of the body near the location of the tumor. As described in those applications, radio frequency energy is applied to the applicators with the result of localized heating in the tumor differentially higher than that of the surrounding normal tissue, heating being continued for a duration and at an intensity sufficient to cause necrosis of the tumor by reason of reaching a temperature therein of about 50.degree. C. However, the heating, in most of the cases involving apparatus in accordance with the previous inventions, has been insufficient to raise the temperature of the surrounding normal tissue so that thermal damage is caused.
In the normal course of operating the radio frequency equipment for the purpose of destroying tumors, differential thermometry is provided so that the difference in temperature between the given tumor and the surrounding tissue can be monitored. This is generally done with non-metallic thermometers having nonelectrolyte fluid such as liquid alcohol filled thermometers. Temperatures as high as 60.degree. C. can be achieved within the tumor while the surrounding normal tissue is heated only to the vicinity of 40.degree. C. under the assumption that about 500 watts of energy at a preferred frequency of 13.56 MHz is employed.
It has been found to be generally desirable to employ radio frequencies which are as low as permissible in order to enhance absorption of energy by the tissues. As a result, the lowest frequencies permitted by the FCC are preferable. The practical frequency range to produce the requisite internal heating for treatment of tumors in accordance with the present invention is from about 100 KHz to about 200 MHz. Since the longer wave lengths are both more effective for heating purposes and are less likely to cause damage by scattering and the like, the preference is distinctly for the longer wave lengths. As previously indicated, the preferred frequency for tumor treatment is 13.56 MHz because this is the longest wave length presently permitted by law.
The apparatus of the previously cited applications have generally utilized powers in the range of 200 to 500 watts. In the present improvement, the power range has been increased to the range of 2 to 4 kilowatts, such range being suitable inasmuch as the applicators are located for the purposes of orbital movement so that the same volumes of tissue will not be exposed to radiation and consequently the actual power conveyed to the patient's body is of the order of 200 to 300 watts. The normal times of exposure to radiation are typically from 10 to 20 minutes, although greater or shorter periods can be employed depending on the size and location of the tumor.
Accordingly, it is a primary object of the present invention to effectuate or carry out treatment on difficult and deep-seated tumors that require long exposure times to radiation and to successfully obviate the problem of excessive heating of the surrounding tissue.
In accordance with the primary feature of the present improvement or invention, the radio frequency, electromagnetic radiation equipment or apparatus is arranged so that the applicators to which a radio frequency generator and amplifier are connected are so arranged that they can be located on opposite sides of the patient's body and along a central axis and to be moved in such a way that the radio frequency energy will be directed at the tumor location but the applicators or plates will be orbited around the central axis so that a given surrounding volume of tissue is not continuously exposed to the RF radiation. Instead, by reason of the orbital movement, only a limited surface area or volume adjacent the tumor is exposed for a predetermined short period of time, the applicator moving continuously away from that given area in its orbital motion.
The above-indicated orbital motion or movement is provided by concurrent application of driving power to a yoke member such that its resultant direction of movement is a combination of movements due to individual force vectors. More specifically, the yoke member is rotated part way about a horizontal axis and concurrently therewith the yoke member is moved in a reciprocating manner, in the plane of rotation. As a result, the combination of movements defines a circular orbital path.
Additionally, the yoke member can be raised or lowered depending upon the location of a given tumor, that is to say, it is elevated from the floor, or table, reference plane a more or less amount. In other words, the yoke member can be adjusted above a horizontal reference plane depending on whether the tumor is toward the anterior or posterior side or part of the patient's body. As far as transverse (X) and longitudinal (Y) coordinates are concerned, the table on which the patient rests can be moved in these directions so as to insure proper alignment of the tumor on the desired axis.
A further fundamental feature of the present invention resides in the concept of combining the tumor treating apparatus with a body scanner device or apparatus. For example, such latter equipment has been described in U.S. Pat. No. 3,839,641 in which there is described a method of an apparatus for the radio nuclide imaging of the whole body of a patient using an unmodified scintillation camera permitting a patient to be continuously moved under or over the stationary camera along predetermined axes. Such a system enables judicious enlargement or enhancement of the image of a particular area of the body, such as an area in which a tumor may be located.
It is well known that there is a detectable amount of radiation from the human body and that tumors radiate more energy than normal tissues because they possess higher base temperatures. In accordance with this knowledge it is possible, using a body scanner, to continuously monitor the condition of a tumor that is being treated by the radio frequency apparatus of the present invention.
As the process of heat treating the tumor proceeds it will be manifest that the absorption of radiation from the RF apparatus will permit an excellent display of the tumor condition as it is being treated, since the absorbed energy will result in a much higher differential temperature in the tumor and consequently a much greater degree of radiation therefrom, compared to normal tissue, when the RF equipment is turned off and the radio active material which has been ingested by the patient is permitted to be monitored by the body scanner.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawing, wherein like parts have been given like numbers.